1. Field of the Invention
The present invention relates to a transmission system and coding communication method for a transmission system, capable of transmitting information by transmitting and receiving signals between a plurality of modules installed at different positions.
2. Related Art of the Invention
For a practical and optimum sophisticated road traffic system to be realized, the following five factors are considered crucial.    1. Possibility of measuring the following distance of vehicles    2. Possibility of drive support    3. Possibility of automatic drive    4. Possibility of communication from the vehicle    5. Possibility of inter-vehicle communication
The situation of the prior art for each of the above-mentioned five factors will be explained.
As to a vehicle for which the following distance is measurable as in (1) above, though not currently available, provision of a laser measuring instrument, an ultrasonic measuring instrument or the like would make it possible to measure the following distance. The measurement of the following distance is indispensable for the factors (2) and (3).
As to the items (2) and (3) above relating to the drive support and the automatic drive, respectively, there is not any means currently available. Research is under way in each organization for a drive support or an automatic drive system with a computer mounted on a vehicle using a method unique to each organization. Details of the research, however, are unknown.
The use of a portable telephone or the like can realize the factors (4) and (5). Also, the radio or the like equipment permits acquisition of information on traffic congestion or the like.
The above-mentioned methods, however, require realization of the five factors separately from each other, and it is impossible to realize an overall efficient road traffic system.
Especially, the factor (4) has no relation with the factors (1) to (3), and it seem that they can be processed independently of each other. If information to be communicated is of the type used with a navigator, however, the factor (4) may be related to the factors (1) to (3). It is not efficient, therefore, to realize the above-mentioned five factor independently of each other but an overall integrated system is desirably built up. By doing so, the road conditions can be accurately grasped, and the information used with the navigator can be generated based on the road conditions, thereby making it possible to supply information much more useful than the information obtained from the CD ROM or the like.
Also, in the case where a vehicle performs a communication, or especially, in the case where information on automatic drive or the like is transmitted or received between the vehicle and other stations, a multiplicity of vehicles running on a road undesirably transmit a high-output radio wave.